BARTALLA, Iraq - Iraqi forces fought their way into militant-held Mosul on Tuesday, the military said, as a top commander declared the "true liberation" of the city from the Islamic State group had begun.

Just over two weeks into the massive offensive to retake Mosul - IS's last major stronghold in Iraq - soldiers managed to push within city limits.

Troops had "entered the Judaidat Al-Mufti area, within the left bank of the city of Mosul," said the Joint Operations Command.

Mosul is split by the Tigris River, with the eastern half of the city known as the left bank. Judaidat al-Mufti is on the southeastern side of the city.

Elite Iraqi forces had also recaptured the key village of Gogjali and taken control of a television station building belonging to a local affiliate of Iraqiya state TV on the eastern edge of the city.

Fighters from the US-trained Counter-Terrorism Service had pushed into the area amid heavy fighting on the eastern front in the past two days.

"Now is the beginning of the true liberation of the city of Mosul," Staff General Taleb Sheghati al-Kenani, the commander of the CTS, told Iraqiya from Gogjali.

"We are working with army units to secure the area and advance on Mosul together," Muntathar Salem, a lieutenant colonel with CTS told an AFP reporter near the front line.

Backed by air and ground support from a US-led coalition, tens of thousands of Iraqi fighters have been converging on Mosul. Some 4,000 to 7,000 militants are believed to be in and around Mosul, where IS chief Abu Bakr al-Baghdadi declared a cross-border "caliphate" after the group seized control of large parts of Iraq and neighbouring Syria two years ago.

Colonel John Dorrian, the spokesman for the US-led coalition against IS, said it had targeted the militants with "nearly 3,000 bombs, artillery shells, rockets and missiles" since the operation began. "We've taken out hundreds of fighters, fighting positions (and) weapons" in the strikes, Dorrian told AFP.

As his forces advanced, Iraqi Prime Minister Haider al-Abadi warned the militants they would have no place to run. "We will close in on (IS) from every place," he said on state television on Monday, dressed in a camouflage uniform. "They don't have an exit, they don't have an escape, they can only surrender - they can die or they can surrender," said Abadi.

Paramilitary forces from the Hashed al-Shaabi (Popular Mobilisation), an umbrella organisation dominated by Iran-backed Shiite militia, launched an assault at the weekend to cut off that route.

They have been advancing north, their sights set on the town of Tal Afar which commands the city's western approaches.

On the northern and eastern sides of Mosul, peshmerga forces from the autonomous Kurdish region have taken a series of villages and towns and consolidated their positions, while federal forces have advanced toward the city from the south.

Iraqi forces are expected to try to open safe corridors for the million-plus civilians still believed to be inside. Humanitarian organisations have been fighting against the clock to build up the capacity to handle the possible mass exodus from the city. The United Nations says up to one million people could be displaced in the coming weeks.

More than 17,900 people have already fled their homes since the operation began, according to the International Organization for Migration.

The UN said Tuesday it had received more reports of IS fighters forcing thousands of civilians into Mosul, possibly to be used as human shields.

The militants also reportedly killed 40 former Iraqi security forces members and dumped their bodies in the river, UN rights office spokeswoman Ravina Shamdasani told reporters in Geneva.

That would bring to 296 the number of former Iraqi security officers killed by IS since last Tuesday, according to the UN.

Up to 600,000 children are among the civilians trapped in militant-held Mosul, Save The Children said on Tuesday, calling for safe corridors as Iraqi forces advanced on the city.

Meanwhile, the Turkish military has deployed tanks and artillery to southeastern districts near the Iraqi border, military sources said Tuesday.

The 30-vehicle convoy left Ankara for Silopi, the sources told AFP, adding that it was now close to Adana province in southern Turkey.

The deployment came as Iraq said its forces had entered jihadist-held Mosul for the first time since the Islamic State group overran the city more than two years ago.

Ankara has repeatedly insisted that it would be involved in the offensive in northern Iraq and would be "at the table".

Defence Minister Fikri Isik said Tuesday's deployment was a part of Turkey's preparation for "important developments in the region", referring to Kurdish rebels inside the country and events in Iraq.

"Turkey is preparing in advance for whatever happens (and) this is one element of that," he said, quoted by the official news agency Anadolu.

The outlawed Kurdistan Workers' Party (PKK) has waged an insurgency inside Turkey since 1984, with almost daily attacks against Turkish security forces in the mainly Kurdish southeast.

Isik added that there was a "serious fight against terror" inside Turkey, a reference to Islamic State (IS) jihadists and the PKK. Last month, Prime Minister Binali Yildirim claimed Turkish artillery hit IS positions in Bashiqa, northern Iraq.

President Recep Tayyip Erdogan Saturday indicated that Turkey wanted to reinforce its security forces already in Silopi in Sirnak province.